Have you ever gone into an underground
mine? If you have, you might have felt that it
got warm as you descended into the ground.
This is exactly what happens in the Earth: It
gets warmer and warmer and warmer.
every kilometer that you descend into the
Earth, the temperature increases by ~25 °C
(or 45 °F). Therefore, 5 km below the Earth,
the temperature can be around 125 °C or 257
°F – beyond the boiling point of water. As
you go deeper, the temperature still
increases. Look at the graph that I added.
shows a temperature profile through the first
250 m below Jericho (in Palestine). You can
ignore all the details, just look at the bold red
line. Now you can read the depth on the y axis
(the downward axis) and the temperature on the x
axis (the axis at the top). You can see that
the temperature gets up to c.a. 1300 °C at 250 km.
If you go down through an ocean rather
than such a continent, you might be at 1300°C
after just ~100 – 125 km. After this, the
temperature still increases and at the center of
the Earth, you get to temperatures bigger than
that is similar to the surface of the sun…
You might know that the core of the Earth is made
of Iron. At this temperature the iron would easily
melt. However, pressure also changes:
The pressure is essentially the weight of
the overlying material. As you go into the Earth,
imagine piling kilometers and kilometers of rock
on top of you. So, the pressure rises and
rises and at the core of the Earth, the
pressure is more than 3 million times the
pressure of the
atmosphere. Because of this high pressure,
the iron in the core cannot melt and behaves as if
it were solid, even though it is more than 5000°C
hot. Let’s say, it wouldn’t be very pleasant to
be down there…
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